U.S. patent application number 14/737827 was filed with the patent office on 2015-12-17 for method for electrochemical modification of liquid stream characteristics.
This patent application is currently assigned to Blue Planet Strategies, L.L.C.. The applicant listed for this patent is Patrick I. James. Invention is credited to Patrick I. James.
Application Number | 20150361570 14/737827 |
Document ID | / |
Family ID | 54835671 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150361570 |
Kind Code |
A1 |
James; Patrick I. |
December 17, 2015 |
METHOD FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAM
CHARACTERISTICS
Abstract
A method for extraction of target components from raw liquid
streams includes steps of providing at least one electrochemical
cell arranged to support redox reactions resulting in
electrochemical change of oxidation states and concentration of at
least one ionized target component, and to control at least one pH
value of at least one electrolyte in the at least one
electrochemical cell; introducing a raw liquid stream comprising a
combination of constituent ionic species into the at least one
electrochemical cell; operating the at least one electrochemical
cell to change concentrations of at least two oxidation states of
at least one targeted ionic species from the constituent ionic
species; operating the at least one electrochemical cell to
maintain a predetermined range of pH of the at least one
electrolyte and to eliminate at least one target component
pertinent to the at least one oxidation state of the targeted ionic
species.
Inventors: |
James; Patrick I.; (Madison,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
James; Patrick I. |
Madison |
WI |
US |
|
|
Assignee: |
Blue Planet Strategies,
L.L.C.
Madison
WI
|
Family ID: |
54835671 |
Appl. No.: |
14/737827 |
Filed: |
June 12, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62011838 |
Jun 13, 2014 |
|
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|
Current U.S.
Class: |
205/573 ;
205/560; 205/574; 205/587; 205/602 |
Current CPC
Class: |
C25B 1/21 20130101; C25B
1/00 20130101; C25C 1/00 20130101; C25B 9/168 20130101 |
International
Class: |
C25C 1/02 20060101
C25C001/02; C25C 1/08 20060101 C25C001/08; C25C 1/10 20060101
C25C001/10; C25C 1/16 20060101 C25C001/16; C25C 1/06 20060101
C25C001/06; C25C 1/12 20060101 C25C001/12 |
Claims
1. A method for extraction of target components from raw liquid
streams using electrochemical cells by manipulation of solvability,
concentrations, and oxidation states of constituents of liquid
streams by electro-effecting controllable changes of electrolytes
pH values, comprising following steps: a) provide at least one
electrochemical cell arranged to support redox reactions resulting
in electrochemical change of oxidation states and concentration of
at least one target component, and to control at least one pH value
of at least one electrolyte in the at least one electrochemical
cell; b) introduce at least one raw liquid stream comprising a
combination of constituent ionic species into the at least one
electrochemical cell; c) operate the at least one electrochemical
cell to change concentrations of at least two oxidation states of
at least one targeted ionic species from the constituent ionic
species, and to controllably change the pH value of the at least
one electrolyte in the at least one electrochemical cell; d)
operate the at least one electrochemical cell to maintain a
predetermined range of pH of the at least one electrolyte and to
aggregate at least a portion of at least one target component
pertinent to the at least one oxidation state of the targeted ionic
species; e) separate and extract at least aggregated portion of the
at least one target component pertinent to the at least one
oxidation state of the targeted ionic species; f) separate and
extract at least a part of reacted products from the at least one
electrolyte in the at least one electrochemical cell.
2. The method for extraction of target components from raw liquid
streams of claim 1; wherein the at least one electrochemical cell
is a Moving Bed Electrode (MBE) electrochemical cell.
3. The method for extraction of target components from raw liquid
streams of claim 2; wherein the Moving Bed Electrode (MBE)
electrochemical cell is a Spouted Bed Electrode (SBE)
electrochemical cell.
4. The method for extraction of target components from raw liquid
streams of claim 1; wherein the oxidation states of ionized
compound have been chosen from the set of ionization states
consisting of Aluminum Al.sup.+3, Cobalt Co.sup.+2, Cobalt
Co.sup.+3, Cuprous Cu.sup.+1, Cupric Cu.sup.+2, Ferrous Fe.sup.+2,
Ferric Fe.sup.+3, Magnesium Mg.sup.+2, Manganese Mn.sup.+2, Nickel
Ni.sup.+2, Nickel Ni.sup.+3, Zinc Zn.sup.+, and Zinc Zn.sup.+2.
5. The method for extraction of target components from raw liquid
streams of claim 1; wherein the at least one compound pertinent to
the at least one oxidation state of the targeted ionic species is
in the form of metal (Mx) hydroxide (Mx.sub.i(OH).sub.j) and
analogous compounds.
6. The method for extraction of target components from raw liquid
streams of claim 1; wherein the at least one raw liquid stream
includes at least one raw Acid Rock Drainage (ARD), acid leachate,
or alkaline leachate.
7. A method for extraction of target components from raw liquid
streams using electrochemical cells by manipulation of solvability,
concentrations, and oxidation states of constituents of liquid
streams by electro-effecting controllable changes of electrolytes
pH values, comprising following steps: a) provide at least one
first electrochemical cell arranged to support redox reactions
resulting in electrochemical change of oxidation states and
concentration of at least one target component, and at least one
second electrochemical cell arranged to control change the pH value
of the at least one electrolyte in the at least one first
electrochemical cell and the at least one second electrochemical
cell; b) introduce at least one raw liquid stream comprising a
combination of constituent ionic species into the at least one
first electrochemical cell; c) operate the at least one first
electrochemical cell to change concentrations of at least two
oxidation states of at least one targeted ionic species from the
constituent ionic species; d) operate the at least one second
electrochemical cell to maintain a predetermined range of pH values
of the at least one electrolyte and to aggregate at least one
target component pertinent to the at least one oxidation state of
the at least one targeted ionic species; e) separate and extract
the at least one target component pertinent to the at least one
oxidation state of the targeted ionic species; f) separate and
extract at least a part of reacted products from the at least one
electrolyte in the at least one first electrochemical cell.
8. The method for extraction of target components from raw liquid
streams of claim 7; wherein the at least one of first and second
electrochemical cells is a Moving Bed Electrode (MBE)
electrochemical cell.
9. The method for extraction of target components from raw liquid
streams of claim 8; wherein the Moving Bed Electrode (MBE)
electrochemical cell is a Spouted Bed Electrode (SBE)
electrochemical cell.
10. The method for extraction of target components from raw liquid
streams of claim 7; wherein the step e) of separation and
extraction the at least one target component pertinent to the at
least one oxidation state of the targeted ionic species is
performed in at least one separate mixing tank arranged to
aggregate at least one targeted component pertinent to the at least
one oxidation state of the targeted ionic species under conditions
of substantially stabile pH values achieved by introduction of at
least one catholyte from the at least one second electrochemical
cell.
11. The method for extraction of target components from raw liquid
streams of claim 10; wherein the step e) of separation and
extraction the at last one targeted component pertinent to the at
least one oxidation state of the targeted ionic species is
performed using at least one separate filtering unit.
12. The method for extraction of target components from raw liquid
streams of claim 7; wherein the at least a part of neutralized
products of step f) comprises strong inorganic acids.
13. The method for extraction of target components from raw liquid
streams of claim 12; wherein the strong inorganic acids include
sulfuric acid, hydrochloric acid, and mixtures of such acids.
14. The method for extraction of target components from raw liquid
streams of claim 7; wherein the oxidation states of ionized target
component have been chosen from the set of ionization states
consisting of Aluminum Al.sup.+3, Cobalt Co.sup.+2, Cobalt
Co.sup.+3, Cuprous Cu.sup.+1, Cupric Cu.sup.+2, Ferrous Fe.sup.+2,
Ferric Fe.sup.+3, Magnesium Mg.sup.+2, Manganese Mn.sup.+2, Nickel
Ni.sup.+2, Nickel Ni.sup.+3, Zinc Zn.sup.+, and Zinc Zn.sup.+2.
15. The method for extraction of target components from raw liquid
streams of claim 7; wherein the at least one compound pertinent to
the at least one oxidation state of the targeted ionic species is
in the form of metal (Mx) hydroxide (Mx.sub.i(OH).sub.j) and
analogous compounds.
16. The method for extraction of target components from raw liquid
streams of claim 7; wherein the at least one raw liquid stream
includes at least one raw Acid Rock Drainage (ARD), acid leachate,
or alkaline leachate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims benefits of
Provisional Application No. 62/011,838, entitled "METHOD FOR
ELECTROCHEMICAL MODIFICATION OF SELECTED LIQUID STREAM
CHARACTERISTICS", filed Jun. 13, 2014. The current application is
also related to co-owned U.S. patent application Ser. No.
13/926,291, entitled "APPARATUS AND METHOD FOR ADVANCED
ELECTROCHEMICAL MODIFICATION OF LIQUIDS"; Ser. No. 13/621,349,
entitled "APPARATUS AND METHOD FOR ELECTROCHEMICAL MODIFICATION OF
LIQUIDS" (resulting in the U.S. Pat. No. 9,011,669); Ser. No.
13/117,769, entitled "APPARATUS AND METHOD FOR ELECTROCHEMICAL
MODIFICATION OF CONCENTRATIONS OF LIQUID STREAMS" (resulting in the
U.S. Pat. No. 8,545,692); Ser. No. 13/251,646, entitled "APPARATUS
FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAMS" (resulting in
the U.S. Pat. No. 8,409,408); Ser. No. 13/020,447 entitled "A
METHOD FOR ELECTROCHEMICAL MODIFICATION OF LIQUID STREAMS"
(resulting in the U.S. Pat. No. 8,262,892); and Ser. No. 11/623,658
entitled "APPARATUS AND METHOD FOR ELECTROCHEMICAL MODIFICATION OF
LIQUID STREAMS" (resulting in the U.S. Pat. No. 7,967,967); all of
the above (the applications and the resulting patents) are
incorporated herein by reference in respective entireties.
FIELD OF THE INVENTION
[0002] The invention relates to a method for improved
electrochemical modification of concentrations of constituents of
liquid streams which contain organic and/or inorganic impurities.
More particularly, the current invention pertains to methods of
application of split compartment electrochemical cells to drive
targeted redox reactions to treat process liquid streams to
directly control their chemistry and to separate and/or convert
constituents (contaminants, solvent, or dissolved additives like
oxygen) into useful byproducts via the treatment.
BACKGROUND OF THE INVENTION
[0003] Contamination of liquid streams with various organic and
inorganic pollutants is a serious global environmental problem
affecting environment quality and represents significant threat to
human health and safety. Substantial metal contamination of aquatic
environments may arise from current or past commercial mining and
metal extraction processes, surfaces modification and protection
processes, or communal and industrial waste sites resulting from a
variety of active or defunct industrial fabrication and
manufacturing activities. Similarly, significant organic water
pollutants, like aliphatic, aromatic, or halogenated hydrocarbons
and phenols are frequently associated with oil exploration,
extraction and refining, chemicals production, manufacturing
processes, or large-scale farming and food processing.
[0004] In addition to potential for significant environmental
damage, polluted liquid streams represent dilute sources of
desirable raw materials like heavy metals and metal oxides. For
example, the Berkeley Mine Pit in Butte, Mont. alone represents an
estimated 30 billion gallons of acid mine drainage which contains
180 ppm of copper along with other metals and thus could yield up
to 22,000 tons of pure copper by use of a small treatment
facility.
[0005] An economically relevant group of prior art methods of
removal of heavy metal ions from liquid solutions is based on
chemical precipitation. This process is generally burdened by
complexity, high cost, clear preference for extremely large
facilities and high-volume operations. Lime neutralization may be
regarded as a dominant treatment approach. In general, several
embodiments of this approach may yield byproducts including
precipitated sludge which may become a concentrated yet mixed
contaminant source of the toxins in the source material. The sludge
mandates further processing and costly long term disposal as a
hazardous waste. Many similar disadvantages burden alternative
heavy ion removal methods that may incorporate: filtration, ion
exchange, foam generation and separation, reverse osmosis, or
combinations of listed processes.
[0006] Considerable market research conducted by many strategic
metal mining and extraction industry consultants indicates that
high grade ore reserves are becoming exhausted, leading world-wide
to generally downward trending ore quality. For example,
practitioners may need a way to use their existing recovery
equipment and processes to recover metals from their often
plentiful but presently unusable low-grade ore or tailings from
legacy operations. Currently, mines may not be capable to
economically process metals when ore sources and/or the resultant
process streams containing the target metal extracted from these
ores are too weak and need strengthening (concentrating) to allow
practical conventional target metal extraction. Thus, the economic
considerations may be closely coupled with technology limitations
providing for continuous motivation to improve all aspects of the
extraction process as measured by cost (capital and operational)
reduction metrics.
[0007] The extraction technologies enabled by several aspects of
the current invention may be adapted to address at least some of
the above considerations. In general, metal extraction methods
based on redox reactions frequently require acidity control and pH
manipulation (such as lowering pH to refresh acid for processing
streams, raising pH to improve processing and/or controllably (and
selectively) drop out contaminants (metals) as valuable products
(hydroxides or other pH sensitive precipitates), or (potentially in
conjunction with pH adjust via counter reaction)--manipulate target
species redox states to improve selected aspects of the target
stream processing. Classic examples may incorporate but are not
limited to conversions of Fe.sup.+3 to Fe.sup.+2, Fe.sup.+2 to
Fe.sup.+3, or Cu.sup.+1 to Cu.sup.+2 and Cu.sup.+2 to
Cu.sup.+1.
[0008] In particular, technologies for capture of mined metals
(e.g. copper processing) from streams frequently include
modification of mining streams (raffinate, wastewater, draindown,
processing bleeds, Pregnant Leach Solution (PLS), and other
stream's chemistry to improve mining productivity. The invention
here affords a new ability to effect and control such modifications
electrochemically to improve processing efficiency and/or
operations.
[0009] Mining influenced waters like Acid Rock Drainage (ARD) and
acid or alkaline leachates (essentially a naturally occurring leach
solution, typically considered wastewater) is often acidic or
alkaline and may contain multiple metals in a high sulfate
background. ARD could also be economically treated using
electrochemical methods of the current invention while achieving
new control and selectivity over solids generation during
treatment.
[0010] Even more particularly, the new method could be employed to
perform or mitigate a number of economically relevant treatments
traditionally accomplished by chemical additions or needs.
Nonexclusive examples include increases of acidity (lower pH)
and/or increase of Fe.sup.+3 concentrations (e.g. for sulfide
leaching) which may enhance leaching processes. Similarly, one may
lower acidity (raise pH) to enhance solvent extraction efficiency
or neutralize streams with potential selective metal (hydroxide)
recovery, or one could lower Fe.sup.+3 content (e.g. converting it
to Fe.sup.+2), to increase the pH of solids formation
(precipitation) (e.g. to avoid scale formation/fouling and/or allow
selective removal), and effect selectivity/efficiency of other
processes like solvent extraction or ion exchange.
[0011] Even further, various methods of the electrochemical pH
adjustment may be utilized in embodiments concerning control of
microbial (viral, bacterial, fungal, protozoal, and macromolecular
including misfolded proteins and other malformed molecules, prions
and fungal prions) infestations. Usage of acidic or alkaline
conditions for control, destruction, sterilization, and or
inactivation of microbiological agents has been well understood by
practitioners. In particular embodiments of the current inventions,
electrochemically generated acidic or alkaline ions may be used to
facilitate effectiveness of added or in-situ generated biocides and
bio-suppressors in addition to being biocidal or bio-suppressive by
itself.
[0012] Generally, electrochemical apparatus and methods in
accordance to the current inventions utilize electricity as
convenient, easily-transportable, and efficiently-controllable
"universal electrochemical agent" used in the desirable
electrochemical reactions (in addition to conventional usage of
electricity only as energy supply). Furthermore, in contrast to
standard precipitation and pH control processes requiring
deliveries of significant amounts of acids, alkalis, and/or salts
(e.g. lime or caustic treatments) various embodiments of the
current inventions enable reduction of disposable byproducts (e.g.
by in-situ recycling and regeneration of desirable components), and
flexibility of process optimization achievable, for example, by
active real time (continuous or batch-to-batch) controlling of
concentrations, flows, efficiencies, and reaction rates of redox
reactions in the targeted electrochemical cells.
SUMMARY OF THE INVENTION
[0013] Current invention relates to a method for extraction of
target components from raw liquid streams using electrochemical
cells by manipulation of solvability, concentrations, and oxidation
states of constituents of liquid streams by electro-effecting
controllable changes of electrolytes pH values. The method of
current invention incorporates steps of: a) providing at least one
electrochemical cell arranged to support redox reactions resulting
in electrochemical change of oxidation states and concentration of
at least one ionized target component, and to control at least one
pH value of at least one electrolyte in the at least one
electrochemical cell; b) introducing at least one raw liquid stream
comprising a combination of constituent ionic species into the at
least one electrochemical cell; c) operating the at least one
electrochemical cell to change concentrations of at least two
oxidation states of at least one targeted ionic species from the
constituent ionic species, and to controllably change the pH value
of the at least one electrolyte in the at least one electrochemical
cell; d) operating the at least one electrochemical cell to
maintain a predetermined range of pH of the at least one
electrolyte and to aggregate at least a portion of at least one
target component pertinent to the at least one oxidation state of
the targeted ionic species; e) separating and removing at least the
aggregated portion of the at least one target component pertinent
to the at least one oxidation state of the targeted ionic species;
and f) separating and extracting at least a part of reacted
products from the at least one electrolyte in the at least one
electrochemical cell.
[0014] An apparatus in accordance with the current invention may
include at least one electrolytic cell having at least one
electrode compartment structured to contain a liquid electrolyte.
The at least one electrolytic cell is structured to support redox
reactions and to generate liquids usable for creating and
maintaining particular concentrations of selected targeted ions
such as Hydrogen ions conducive for applications such as the
precipitation of targeted materials in internal or separate
reactors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other embodiments, features, and aspects of
the present invention are considered in more detail in relation to
the following description of embodiments shown in the accompanying
drawings, in which:
[0016] FIG. 1. is a schematic cross-sectional side view of devices
in accordance with prior art.
[0017] FIG. 2. is a graphic illustration of particular features in
accordance with prior art.
[0018] FIG. 3. is a schematic illustration in accordance with one
embodiment of the current invention.
[0019] FIG. 4. is a schematic illustration of one embodiment of the
current invention.
[0020] FIG. 5. is another schematic illustration of one embodiment
of the current invention.
[0021] FIG. 6. is a graphic illustration of particular features in
accordance with current invention.
[0022] FIG. 7. is a schematic illustration of one embodiment of the
current invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The invention summarized above may be better understood by
referring to the following description, which should be read in
conjunction with the accompanying drawings. This description of an
embodiment, set out below to enable one to build and use an
implementation of the invention, is not intended to limit the
invention, but to serve as a particular example thereof. Those
skilled in the art should appreciate that they may readily use the
conception and specific embodiments disclosed as a basis for
modifying or designing other methods and systems for carrying out
the same purposes of the present invention. Those skilled in the
art should also realize that such equivalent assemblies do not
depart from the spirit and scope of the invention in its broadest
form.
[0024] It may be generally recognized that operation of
electrochemical cells is based on redox reactions and can employ
cells which can occur in many forms. In general, the class of split
compartment cells (SCC) (in their multitude of forms) can provide
examples of suitable apparatus to accomplish the current method
disclosed herein. One such relevant example typical of the class of
Moving Bed Electrode (MBE) cells may be represented by the specific
example from the subset of Spouted Bed Electrode (SBE) cells as
disclosed in the above incorporated (by the reference in the
opening paragraph) U.S. Pat. No. 7,967,967 and schematically
illustrated in the FIG. 1. The one embodiment of an SBE cell of
prior art provides a single, but nonexclusive example of a device
suitable for use in the current method for illustrative purposes
and may include of one or more anodes 10 coupled to one or more
high surface area cathodes 20, here in the form of a spouted moving
particulates bed, separated by a distance. Catholyte flow 30 of
liquid electrolyte catholyte 24, driven by an external catholyte
pumping station 40, is directed through the high surface cathode 20
to achieve vigorous convection in the particulates bed to
facilitate a high degree of electrode utilization. Unidirectional
current is fed into the cell via anode current feed 50(+) and out
via cathode current feeder device 90 and cathode current feed
50(-). The cell illustrated in the FIG. 1. is shown in a simple
double chamber planar configuration comprising cathode cell chamber
60 and anode cell chamber 70 (generally containing electrolytes,
catholyte 24 and anolyte 14 respectively) each pair of which is
separated by a separator allowing ionic conduction (a porous or
selective membrane for example) 80 which directs the bulk flows of
electrolytes (catholyte 24 and anolyte 14) while maintaining
intimate electrochemical contact between the separated cathode 20
and anode 10 via ionic conduction. The authors note that other cell
configurations (stacked, cylindrical, etc.) could readily also be
employed and that cells employing multiple and additional chambers
may be of the same or different configurations and employ the same
or different cathodes 20, anodes 10, and separators 80 as desired
by a specific situation. Depending upon the state of control valve
system 85 the cell can operate in a batch mode processing the fluid
contained in the reservoir 97, or in a flow-through mode modifying
liquid streams delivered by external pipelines 95.
[0025] It is well-understood that the operation of a SCC cell may
be based in redox chemical reactions generally resulting in changes
of pH values of the anolyte 14 from relatively high input
(beginning value in the batch operation embodiments) value to
relatively lower output value (ending value in the batch operation
embodiments), while in opposition, the catholyte 24 may be reacted
from respective states of relatively low pH into states of
relatively high pH values. It may be noted that such acidity
changes may be controlled by the specific design and components of
the apparatus, control of the fluid flows and electrical discharge
parameters. It may be additionally noted that, by arranging and
controlling of transport (motions and reactions) of charged species
(e.g. ions and electrons) through any simple or composite
(multi-chamber) cell one can change oxidation states and/or pH of
the electrolytes (and other compounds) in the pertinent chambers of
the particular electrolytic cell. Thus, in the simple example in
FIG. 2, one may note that the electrochemical redox process
generally increase acidity (reduce pH) of the anolyte 14, while
simultaneously increasing alkalinity (increasing pH) of the
catholyte 24.
[0026] For example, at the cathode 20 the pH might be raised by
proton reduction and hydrogen formation (typical--water splitting
at elevated pH or acid neutralization at low pH Eqs. (1)-(3)).
Alternatively, oxygen reduction might be targeted to generate
alkaline hydroxide or even a potential reactant like hydrogen
peroxide (which can then be used as an oxidant or a reductant
depending on the detailed chemistry created).
TABLE-US-00001 CONDITIONS 2H.sup.+ + 2e.sup.- .fwdarw. H.sub.2(g)
(1) ACID H.sup.+ + H.sub.2O + 2e.sup.- .fwdarw. H.sub.2(g) +
OH.sup.- (2) Neutral/Alkaline O.sub.2 + 2H.sub.2O + 4e.sup.-
.fwdarw. 4OH.sup.- (3) Neutral/Alkaline
[0027] The devices and methods of several embodiments of the
current invention may be understood using the above concepts of
electrochemical controlling of the acidity of pertinent
electrolytes and the oxidation states of selected constituents for
treatment of preexisting liquid media and/or ad hoc prepared
solutions using electricity. More particularly, in some embodiments
one or more electrochemical cells may be used singularly or in
combinations to separately, simultaneously, or combinations
thereof, control pH values of the electrolytes, generate particular
oxidation states of the constituents, and act as a reactor for
targeted chemical reactions (e.g. precipitation of particular metal
hydroxides).
[0028] One exemplary application concerning methods of
electrochemical treatment of ARDs incorporating concentrations of
aluminum ions and various oxidation states of Fe ions is given
schematically in FIG. 3. The illustrated example includes raising
the pH of an incoming typical raw target ARD stream (acidic, pH
.about.1 and containing a combinations of metals including ferric
ion (Fe.sup.+3) and aluminum (Al.sup.+3)) in a controlled and
staged fashion to enable enhanced and selective metal recovery via
hydroxide driven sequential precipitation of the target metals. It
also notes the concurrent acid generation in the anolyte as a
potentially useful byproduct of the targeted reduction reactions in
the catholyte. At each electrode single or multiple reactions can
be targeted to be driven either essentially sequentially or
simultaneously within one or more of the electrochemical cells or
cell chambers within a given cell. For example, initial reduction
of the catholyte ferric (Fe.sup.+3) to ferrous (Fe.sup.+2) (with
concurrent anolyte acid generation) as an alternative and
additional reaction to the catholyte proton elimination at the
cathode is noted as a specific embodiment of the disclosed
method.
[0029] FIG. 3 illustrates the application and utility of the
disclosed method for the specific exemplary embodiments, not
exclusive of other applications, of treatment of ARD's by
electrochemical tailoring the oxidation state of selected
contaminants and also the overall solution pH. Depending upon
particulars of different embodiments several different metal ions
and ionization states including (but not limited to) Aluminum
Al.sup.+3, Cobalt Co.sup.+2, Cobalt Co.sup.+3, Cuprous Cu.sup.+1,
Cupric Cu.sup.+2, Ferrous Fe.sup.+2, Ferric Fe.sup.+3, Magnesium
Mg.sup.+2, Manganese Mn.sup.+2, Nickel Ni.sup.+2, Nickel Ni.sup.+3,
Zinc Zn.sup.+, and Zinc Zn.sup.+2 may be present.
[0030] The initial step 310 of FIG. 3 includes introduction of raw
target stream (here acidic ARD) into the cathode chamber of
electrochemical cell EC-1 arranged here for catholyte ferric
reduction in preference to catholyte proton reduction. The
separated chamber nature general to split compartment cells,
(recall the general class of applicable electrochemical cells noted
in paragraph [0022]) such as the specific SBE version used here for
illustration, may limit significantly bulk electrolyte mixing. This
may minimize parasitic counter reaction losses (i.e. neutralization
of anode generated protons by cathode proton consumption and by
reacting with cathode generated hydroxide or similarly anode
oxidation of cathode generated catholyte ferrous (Fe.sup.+2) and
anode regeneration of ferric (Fe.sup.+3). Removal of ferric
(Fe.sup.+3) in step 310 reduces the possibility of ferric
oxyhydroxides like ferric hydroxide (Fe(OH).sub.3) precipitation at
pH .about.3, thus clearing the way for subsequent metal
oxyhydroxide precipitation step 320. Step 320 of precipitation and
extraction of other metal oxyhydroxides like Al(OH).sub.3 may be
achieved by controlling the pH (for this embodiment to about
pH.about.5) in a reactor using product catholyte from cell EC-2.
Subsequently, in Step 330 separate precipitation of Fe(OH).sub.2
may be conducted in a reactor characterized by relatively reduced
acidity (e.g. having substantially neutral pH.about.8) through use
of product catholyte from cell EC-3. Following step 340 may include
separation of additional metal oxihydroxides from alkaline
solutions (e.g. pH .about.11) produced using product catholyte from
cell EC-4 and outputting of the resulting alkaline liquid products
for other uses and/or reusing all or part of it as constituents of
electrolyte feedstocks for cells EC-X where X=1 to 4. A
non-exclusive reuse example for the neutralized or acidic products
may be to chemically leach additional metals out of predisposed
materials (natural or man-made deposits of low grade ores or
similar).
[0031] One embodiment of a processing device in accordance with the
above processing scheme has been illustrated in FIG. 4. The device
of the illustrated embodiment has been arranged to receive external
unprocessed ("raw") liquid stream ("Acidic Raw Target Stream")
preferably into the at least one cathode cell chamber 60 of at
least one electrochemical cell EC-1 410 for predominantly the
reduction of the Fe.sup.+3 to the Fe.sup.+2 oxidation state. In
particular embodiments, one or more high surface area cathodes 20
in the form of a spouted particulates bed may be utilized at least
because of relatively high specific electrode surface area
well-suited for efficient contacts to the cathode current feeder
device 90 and the catholyte stream 24. In the particular
embodiment, the electrochemical cell EC-1 410 may be arranged to
diminish collection of the products of the redox reactions on the
electrode surfaces ("electrode plating") in at least to facilitate
stability and uniformity of the cell operations.
[0032] The resulting catholyte processed by the cell EC-1 410 may
be transferred into at least one separate first mixing tank 420 for
precipitation of Al(OH).sub.3, Al(OH) (SO.sub.4), or analogs at the
pH.about.5. The desired moderate acidity (pH.about.5) conducive to
essentially complete precipitation of the Al(OH).sub.3 analog
compounds (analogs) may be created and maintained using resulting
catholyte from the cell EC-1 410 potentially mixed with the higher
pH catholyte from another electrochemical cell EC-2 430. In the
particular embodiment, the electrochemical cell EC-1 410 may also
be arranged for the efficient conversion of other reducible species
than protons (such as Fe.sup.+3 to Fe.sup.+2 here), while the
electrochemical cell EC-2 430 may be arranged for generation of
higher pH catholyte sufficient to maintain substantially stable pH
(e.g. pH.about.5) in the first mixing tank 420. The precipitated
Al(OH).sub.3 and/or analog compounds may be separated and removed
by various means, for example, by filtration in first filtering
unit 440. It may be noted that, at least for the purpose of the
current application, the analog compounds (analogs) have been
defined as all forms and mixtures of related inorganic and organic
compounds including but not limited to simple and complex inorganic
or organic hydroxides and associated salt; hydrated hydroxides and
salts incorporating one or more water molecules; monomers, dimmers,
oligomers, and polymers incorporating hydroxides or salts;
coordination complexes; compounds including polyoxometalates;
colloidal and hydrocolloidal aggregates; and mixtures and
combinations of above.
[0033] Subsequently, filtrate solution from the first filtering
unit 440 may be transferred to second mixing tank 450 for
subsequent precipitation of other components (here noted as
Fe(OH).sub.2 at the pH.about.8). The desired acidity (pH.about.8)
conducive to precipitation of the Fe(OH).sub.2 analog in mixing
tank 450 may be created and maintained using resulting higher pH
catholyte from another electrochemical cell EC-3 470 arranged for
generation of the anolyte having desired concentration of hydroxyl
ions and potentially in-mixed with the filtrate solution from
filtration unit 440. The ferrous hydroxide Fe(OH).sub.2 analog
compound may be in turn separated by filtration in second filtering
unit 460.
[0034] Similarly as above, the filtrate from the second filtering
unit 460 may be transferred to third mixing tank 480, where
additional metals may be precipitated, for example at pH.about.11
such as is typical of conventional mixed ion precipitation used in
wastewater treatment, and separated by third filtering unit 485.
Additional or less mixing tanks and precipitation stages to further
sub-divide the process as desired to fit specific target
chemistries could also be readily employed. The desired pH
(.about.11) may be maintained using higher pH catholyte from yet
another electrochemical cell EC-4 490, optimized to maintain
pH.about.11 in the mixing tank 480. At such alkalinity, many metal
hydroxides and associated compounds may be precipitated (and
subsequently removed e.g. by the filtering unit 485) resulting in
the substantially metal pollution free filtrate solution containing
little residual metals to generate fouling solids in the high pH
catholyte circuits of EC-2, EC-3, and EC-4. Accordingly, the
filtrate can be used to support the catholytes of the
electrochemical cells EC-2 430, EC-3 470 and EC-4 490. Similarly,
filtrate solution from the filtering unit 485 may also be utilized
to support anolytes in the electrochemical cells 430, 470, and/or
490.
[0035] Another class of embodiments has been schematically
illustrated in FIG. 5. In such embodiments, separated
electrochemical cells EC-2 430 and EC-3 470 have been replaced by
at least one compounded electrochemical cell EC-N 510 including a
plurality of chambers. The cell EC-N 510 may be structured to
generate a plurality of electrolytes arranged to maintain
prearranged pH in more than one mixing tank (e.g. mixing tank A 520
and mixing tank B 530). In the illustrated embodiments, at least
one mixing tank (e.g. mixing tank A 520) may be arranged in a
proximity to the electrochemical cells. It should be noted that the
special proximity may not necessitate the proximity of pH values of
the mixing tanks and the electrolytes as the precipitation pH
values in the mixing tanks may be influenced by the acidity
(alkalinity) of the input and output processing streams. It should
be also noted that the mixing tanks in different embodiments may be
structured as external or internal subassemblies of the
electrochemical cells (e.g. 430 or 510) at least for reduced
circulation complexity and losses. Also, cells may incorporate one
or more separators (e.g. first, second, or third separator 530-550
separately or in combinations) which may or may not each employ
different or the same separating mechanisms. One may note that
separators 530-550 may not be limited to filtering units only. Any
method (mechanical, hydraulic, electrostatic, electromagnetic,
gravitational or combined) may be utilized in different embodiments
to separate desired products of reactions in mixing tanks (e.g.
metal Mx hydroxides Mx.sub.i(OH).sub.j and associated analogs).
[0036] The example of precipitation of various different
commercially valuable metal hydroxides may be further elaborated on
the basis of the idealized representative Metal Hydroxide
Solubility vs. pH graphs exemplified in FIG. 6 and summarized in
Table 1 (adopted from Chapter 7 of The International Network for
Acid Prevention INAP web page starting at:
guide.com/index.php?title=Main_Page Jun. 1, 2014).
TABLE-US-00002 TABLE 1 Metal Raffinate Precipitation pH Range
Ferric iron, Fe.sup.3+ 2 to 3 Aluminum, Al.sup.3+ 3 to 4 Copper,
Cu.sup.2+ 6 Ferrous iron, Fe.sup.2+ 6.5 to 7.5 Zinc, Zn.sup.2+ 7
Nickel, Ni.sup.2+ 7.5 Cobalt, Co.sup.2+ 8.2 Manganese, Mn.sup.2+
8.6 Magnesium, Mg.sup.2+ 9
[0037] As discussed above, the electrochemical cells can be
separate (e.g. 430, 470, or 490) or composite (510) and/or arranged
to perform single or multiple functions in a single unit. The
target contaminant (metals) separation can be effected singly,
sequentially, or in conjunction with manipulation of the specific
target materials being controlled through the operation of the
electrochemical cell and mixing condition details. The separation
can be effected solely by the electrochemical cell or in
conjunction with additives (e.g. adding ozone at elevated pH to
oxidize Mn or other additives to facilitate desired processing or
sulfide derivative compounds to achieve pH sensitive metal sulfide
precipitation to further refine target product separation). In
different embodiments of the present invention, ozone or other
desired products comprised of oxidants or reductants may be
generated via at least one electrochemical cell (either in-situ,
like EC-1 410 or separately but on site as with EC-2 430 and/or
EC-N 510. The specific location of production within the cell
depends upon whether the product is generated through a reduction
or oxidation reaction. It is noted that some compounds (like
hydrogen peroxide) may be both oxidizers or reducers depending on
specific chemistry details and can be generated at either the anode
or cathode depending on how the detailed electrochemistry chemistry
is controlled.
[0038] In particular embodiments exemplified by the schematics in
FIG. 4, the at least one electrochemical cell EC-1 410 may be
arranged to perform both pH alteration and another targeted redox
reaction (here Fe.sup.+3 to Fe.sup.+2) concurrently, whereas the
electrochemical cells EC-2 430, EC-3 470, and/or EC-4 490, may be
arranged and optimized to perform dominantly pH adjustment and
sustainment. Chemically, one of the differences between these
electrochemical cell groups may include: the case where the
neutralization reaction can occur outside the cell by leveraging
the water neutralization reaction (that is, the electrochemical
cell product may be in effect a proxy for the actual targeted goal
so it can be made in one spot and used in another.) This may be
especially significant with a redox reaction involving ozone or
peroxide, for example. Another feature may concern the situation
wherein the pH reaction may utilize water as a reactant and thus in
aqueous solution effectively has a nearly unlimited supply of
reactant whereas other redox species one might target are limited,
and get depleted in the cell such that other reactions begin to
occur. Such feature may provide opportunity to recycle target ions
in a fashion improving process practicality. For example, sodium
acting as a supporting electrolyte effectively acts as a carrier
(charge balance) for generated hydroxide and can be reused since it
is not precipitated in the target pH range. Thus, in comparison to
costly NaOH (caustic soda) addition, the electrolytic process may
allow effective refreshing of the neutralizer where the sodium is
recycled through the process and new hydroxide is generated,
thereby lowing chemical feedstock input needs and significantly
improving process practicality.
[0039] A multitude of potential separations/recoveries may be
structured as separate embodiments or in combinations. An exemplary
subset may include metal hydroxide separations where the target
metals can selected through a combination of tailored solution
constituent redox state and solution pH conditions generated as a
result of the electrochemical treatment. Common representative
metal hydroxide examples may be seen in FIG. 6 and Table 1 (e.g.
aforementioned separation of Al.sup.+3 from a mixture of Fe.sup.+2
and Fe.sup.+3 via reduction of Fe.sup.+3 to Fe.sup.+2). It should
be also noted that the process using reduction of Fe.sup.+3 to
Fe.sup.+2 may be proffered as the direct separation of Fe.sup.+3
from Al.sup.+3 may be less practical because of proximity of
pertinent pH precipitation ranges (FIG. 6 and Table 1).
[0040] In addition, a variety (or mixture) of acids could be
generated in different embodiments. Embodiments generating sulfuric
acid may be of particular interest since the raw target stream
sources including sulfate may be very common. Also, embodiments
including seawater application as the raw target stream (which the
mining industry may be increasingly utilizing) may generate
HCl--should that be of interest. Furthermore, the initial input
stream could start at higher, near-neutral, or even alkaline pH
with the process reversed--treatment lowers input stream pH to
effect targeted separations within the anolyte and the "byproduct"
may be now a strong base (catholyte) where Mx(OH).sub.N could be a
variety of Mx and N combinations where Mx(OH).sub.N may be highly
soluble (including alkali metals and ammonium or organics cations).
An example and nonexclusive application embodiment would be the
treatment of drainage from coal mining sites which is known to
occur in many forms with a bimodal pH distribution, sometimes being
acidic and other times being alkaline.
[0041] FIG. 7. schematically illustrates particulars of an example
acid leaching process in accordance with one class of embodiments
of the current invention. It should be noted that different
embodiments may utilize essentially reversed process (relative to
the illustration in FIG. 7) for alkaline leaching, when desirable.
In FIG. 7, the leach solution 710 is passed to the at least one
anode cell chamber 70 arranged to generate acid and combined with
material to be leached (either in-situ, for example in at least one
dedicated volume 720 or externally, for example in at least one
separated reactor 730). Subsequently (after the leaching has been
effected) the spent leached material may be separated from the
anolyte, for example by at least one separator 740. The pregnant
(leached component laden) anolyte 14 may be passed to at least one
cathode cell chamber 60 for leached material recovery. Leached
material could be directly plated (electrowon) or precipitated via
electrochemical pH adjustment or other electrochemical
manipulations (e.g. internally in at least one mixing volume 750 or
externally in at least one separated reactor 780) and separated by
at least one separator 790. The barren raffinate 760 (leach
solution from which the majority of the leached component was
removed), may be subsequently returned to the at least one anode
cell chamber 70 where the acid and material to be leached may be
replenished for another circuit through the system. The leached
component 770 (to be recovered) may also be recovered ex-situ by
non electrochemical means and, depending upon particular
embodiments, by any of the number of embodiment-specific recovery
methods.
[0042] The present invention has been described with references to
the exemplary embodiments arranged for different applications.
While specific values, relationships, materials and components have
been set forth for purposes of describing concepts of the
invention, it will be appreciated by persons skilled in the art
that numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the basic concepts and operating
principles of the invention as broadly described. It should be
recognized that, in the light of the above teachings, those skilled
in the art can modify those specifics without departing from the
invention taught herein. Having now fully set forth the preferred
embodiments and certain modifications of the concept underlying the
present invention, various other embodiments as well as certain
variations and modifications of the embodiments herein shown and
described will obviously occur to those skilled in the art upon
becoming familiar with such underlying concept. It is intended to
include all such modifications, alternatives and other embodiments
insofar as they come within the scope of the appended claims or
equivalents thereof. It should be understood, therefore, that the
invention may be practiced otherwise than as specifically set forth
herein. Consequently, the present embodiments are to be considered
in all respects as illustrative and not restrictive.
* * * * *